Early Tissue Reactions - Chapter 8

Somatic Effects

• Effects on the body that was irradiated.
• Classified as early or late effects.
• Somatic tissue reactions are dose-related, leading to cell death (deterministic effects).
• These effects have a threshold; biologic damage depends on the absorbed dose.

Early Tissue Reactions

• Appear within minutes, hours, days, or weeks after exposure.
• Severity is dose-dependent (more dose = more severe effects).
• Caused by cell death.

Possible High Dose Consequences

• Nausea, fatigue, erythema, epilation.
• Blood and intestinal disorders, fever.
• Dry and moist desquamation.
• Depressed sperm count, temporary or permanent sterility.
• Central nervous system injury (at extremely high doses).

Acute Radiation Syndrome (ARS)

• Occurs after large whole-body doses (\geq 6 \text{ Gyt}) delivered in a short period.
• Includes Hematopoietic, Gastrointestinal, and Cerebrovascular syndromes.

ARS Stages

• Prodromal: Immediate response of radiation sickness.
• Latent: No signs of sickness (false sense of well-being).
• Manifest illness: Symptoms return, more severe.
• Recovery or death: Outcome depends on dose; sublethal doses may allow recovery.

Hematopoietic Syndrome

• Doses of 1 to 10 Gyt.
• Bone marrow is the most radiosensitive vital organ system.
• Death occurs due to bone marrow destruction: anemia, infection.
• 1-2 Gyt: Individuals can survive.*
• 2-10 Gyt: All individuals will die.

Gastrointestinal Syndrome

• Threshold dose of approximately 6 Gyt.
• Death occurs 3-10 days post-irradiation without medical support.
• Symptoms: nausea, vomiting, diarrhea, leading to death from infection, fluid loss, and electrolyte imbalance.

Cerebrovascular Syndrome

• Doses of 50 Gyt or more to the central nervous system.
• Death occurs within hours to 2-3 days post-irradiation.
• Symptoms: nervousness, confusion, severe nausea, vomiting, diarrhea, loss of vision, burning sensation of the skin, and loss of consciousness leading to shock, agitation, ataxia, edema, fatigue, lethargy, seizures, meningitis, respiratory distress, coma, etc
• Injured blood vessels and capillaries permit fluid to leak into the brain, increasing intracranial pressure, and causing tissue damage

Acute Radiation Syndrome Overview

• Hematopoietic: 1-10 Gyt, 6-8 weeks survival.
• Gastrointestinal: 6-10 Gyt, 3-10 days survival.
• Cerebrovascular: 50+ Gyt, hours to 2-3 days survival.

Radiation Disasters

• Chernobyl: Explosion at Chernobyl nuclear power plant in Pripyat, Ukraine - 1986
• Hiroshima and Nagasaki: Atomic bombing in Japan resulted in ARS, late effects (cataracts), and stochastic effects (leukemia).

Lethal Dose

• LD 50/30: Dose lethal to 50% of the population within 30 days (3.0-4.0 Gyt).
• LD 50/60: Dose lethal to 50% of the population within 60 days (more accurate for humans).

Skin Effects

• Radiodermatitis: Reddening of the skin from excessive exposure.
• Skin is relatively radiosensitive due to continuous regeneration.
• 2 Gyt can cause skin erythema within 24-48 hours.
• Desquamation: Shedding of skin outer layer; moist then dry.
• Epilation: Hair loss from radiation exposure.

Reproductive System Effects

• Human germ cells are radiosensitive.
• 0.1 Gyt can affect sperm count (males) and menstruation (females).
• Spermatogonia stem cells continually reproduce, oogonia ovarian stem cells multiply only during fetal development before birth, and steadily decline throughout life.

Hematologic Effects

• Pluripotential stem cells determine cell development (lymphocytes, granulocytes, thrombocytes, erythrocytes).
• Blood counts used to monitor occupational radiation exposure in the 1920s and 1930s.

Cytogenetic Effects

• Cytogenetics: Study of cell genetics and chromosomes.
• Karyotype: Chromosome map for analysis.
• Metaphase: Phase of mitosis to evaluate chromosome damage.
• Chromosome and chromatid aberrations observed.